Extending the snowflake schema
The company is thinking about extending their business beyond bookstores in Canada and the US. Particularly, they want to expand to a new continent. In preparation, you decide a continent field is needed when storing the addresses of stores.
Luckily, you have a snowflake schema in this scenario. As we discussed in the video, the snowflake schema is typically faster to extend while ensuring data consistency. Along with dim_country_sf, a table called dim_continent_sf has been loaded. It contains the only continent currently needed, North America, and a primary key. In this exercise, you'll need to extend dim_country_sf to reference dim_continent_sf.
Deze oefening maakt deel uit van de cursus
Database Design
Oefeninstructies
- Add a
continent_idcolumn todim_country_sfwith a default value of 1. Note thatNOT NULL DEFAULT(1)constrains a value from being null and defaults its value to1. - Make that new column a foreign key reference to
dim_continent_sf'scontinent_id.
Praktische interactieve oefening
Probeer deze oefening eens door deze voorbeeldcode in te vullen.
-- Add a continent_id column with default value of 1
ALTER TABLE ___
ADD ___ int NOT NULL DEFAULT(1);
-- Add the foreign key constraint
ALTER TABLE ___ ADD CONSTRAINT country_continent
FOREIGN KEY (___) REFERENCES ___(___);
-- Output updated table
SELECT * FROM dim_country_sf;